Automatic milking systems (AMS) are well known in the art. The current implementations of AMS are almost entirely with cows held indoors. Cows are bedded and fed in a large barn that also houses the AMS. Cows learn to circulate freely the short distance between their cubicles and the AMS unit, a prime motivator being in-bail feeding while they are being milked in the AMS. The cows only need to move comparatively short distances, perhaps 20-30 m within the housing system to the AMS.
Many cows around the world are not housed in this fashion, however, but freely graze pasture. In New Zealand and Australia, in particular, there is no housing of cows; they spend all their time on pasture. These pasture-based systems are very extensive and often require the cows to walk considerable distances to be milked in conventional milking systems. This can be up to 2-3 km walking distance, and they normally do this twice a day. Voluntary milking systems, which cows visit on a voluntary basis, have become increasingly common during the last years. In such systems cows are monitored and are given milking permission on an individual basis.
WO 03/000044 discloses a selection system for milking animals which could enable an automatic milking system (AMS) to be efficiently used in extensive grazing husbandry. Lactating animals, for example cows, are attracted to a drinking station from a grazing paddock. As cows come to drink at the drinking station, they are identified and checked against milking records. If a cow meets a predefined criterion, it is directed to a milking area which could include an automatic milking system. If a cow does not meet a predetermined criterion, the cow is directed back to the paddock from where it came.